ML20003A262

Forwards Supplementary Info Re Spent Fuel Pool Mod,In Support of Installation of high-density Borated Spent Fuel Storage Racks.Info Confirms Structural Integrity of Racks. NRC Concurrence & Revised Safety Evaluation Requested

ML20003A262
Person / Time
Site:	Calvert Cliffs
Issue date:	01/29/1981
From:	Lundvall A BALTIMORE GAS & ELECTRIC CO.
To:	Clark R Office of Nuclear Reactor Regulation
Shared Package
ML20003A263	List: ML20003A262 ML20003A264
References
NUDOCS 8102030274
Download: ML20003A262 (7)

Text

- k BALTIMORE GAS AND ELECTRIC COMPANY P. O. BOX 1475 BALTI M O R E. M A RYLA N D 21203 Aarwua c.Lunov m aa. January 29, 1981 v.c p...... e s-Office of Nuclear Reactor Regulatica U.S. Nuclear Regulatory Canmission Ashington, D.C. 20555 ATTN

Mr. Robert A. Clark, Chief Operating Reactors Branch #3 Division of Licensing

Subject:

Calvert Cliffs Nuclear Power Plant Units Nos. 1 & 2, Dockets Nos. 50-317 & 50-318 Spent Fuel Pool Modificatien Supplementary Infor. nation

References:

(a) BG&E letter dated 7/3/79 fran J. W. Gore, Jr. to H. R.

, rc Denton, Request for Amendment.

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& d (b) 3G&E letter dated 1/15/80 fra: A. E. Lundvall, Jr., to F~ > R. W. Reid, same subject.

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h - " (c) NRC letter dated 9/19/80 from R. A. Clark to A. E.

^

'l_ Lundvall, Jr., Amendment A7 and #30 for Units 1 & 2, e,'. respectively.

(d) Telephone conversation on 1/27/81 between BG&E (R. F.

@ Ash, M. C. Key, R. C. L. Olson) and NRC (E. L. Conner, I ,

A. Hafiz)

F Gentfsnen:

References (a)and(b),assupplemented,requestedapprovalforthe installation of high-density borated spent fuel storage racks for Calvert Cliffs Units # 1 & 2. NE approval of this request was forwarded by reference (c) as Amendment A7 and #30 for Units #1 & 2, respectively along with the NBC's Safety Evaluation. Subsequent conversations with your Staff have re-vealed that certain design aspects of the as-built racks are not as documented in the above references. Specifically, two areas of concern exist:

1) The above references indicated that the racks were designed and

' fabricated in accordance with ASME Boiler and Pressure Vessel Code, Subsection NF. This is true except for the use of spot welds and two other areas of clarification. Spot welding was done in accordance with the AISC Specification as discussed in Enclosure (1). The two areas of clarification, weld rod composition and material traceability, are also discussed in Enclosure (1). The latter of these was previously discussed with your staff, Ref. (d);

g] O' C o 0MN [

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January 29, 1981

2) Inspecticus indicated that a limited number of defective welds may exist in the racks. Further testing and calculatiens have since demcastrated the structural inte5rity of the racks. We have kept the NRC I & E Resident Inspector apprised of this situation. Enclosure (2) is an Evaluation of the Defective Welds.

Our evaluation of these two concerns, as supported in the E= closures, conclude that no safety hazard exists. We request NRC review and concurrence, and that a revised Safety Evaluatic.1 be issued if appropriate.

Very truly yours,

/

5 71ce Presideht Supply I {-

cc: J. A. Biddisen, Esquire G. F. Trowbridge, Esquire Mr. E. L. Conner, Jr. - NRC .

Mr. R. A. Milos - NES Mr. R. E. Architzel - NRC i

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Enclosure 1 age 1 of 5 CCHFCRMANCE CF CALVERT CLI3TS, UNIT 1 SPINT FUEL 3 ACES TO ASME AND AISC CCDE RKUIMCS

1. DESIGN AND FA3RICATIm RKUIRDE3TS __

In its position paper for the review and acceptance cf spent fuel rack design a:xi fabrication , the NRC has stated that the perfor=ance basis for the design, fabrication and installatien cf spent fuel racks =ay be either 1) the AISC Specificatien2 cr, 2) Subsection NF cf the ASME Code 3 for Class 3 ccupene=t supports. The two design approaches are essentially ide=tical when i=plemented in the NRC positica paper, since the ASME Code Design is based en the linear elastic analysis =ethods of Appe@ r X7II cf the ASME Code and these =ethods have been derived directly frcm the AISC Specification. --

NES favers using the AISC Specificatien because it is =cre directly applicable to fuel rack structures rather than using the ASME Code, which is acre applicable to pressure vessels, piping, and their rapperts.

For Calvert Cliffs, Unit 1, however, NES agreed to design and fabricate the spent fuel racks to the ASME Code procedures but to linit material traceability to the use of certified materials and the delta ferrite requirements to weld rod test certifications. See paragraphs Ea & 2d below.

2. APPLICAmTT! AND CCNFCPVANCE TO CCDE RKUr4EMENTS The AISC Specification is intended specifically for structural steel for buildings while Subsection NF is intended for nuclear ccupenent supperes. The following paragraphs rhze NES' design and fabricatica confer =ance to both the AISC specificatiens and Subsection NF.

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Paga 2 of 5

a. Ma.terials . _ . _ _

The AISC Specification allevs only the use of structural carbon steel and welding rods that confoms to specific ASTM and AWS types. In accordance with NBC position, the use of stainless steels is acceptable, provided its use is in conjunction with the AISC Specificatien and that correct material properties are used in conjunction with the design calculations.

b. Cold-Fomed Steel Design

, The cold-fomed stainless steel thin walled fuel storage cells used in the Calver. Cliffs Unit i rack design are not ecvered directly by ASME Subsection NF, including Appendix XVII. It is more appropriate for this rack design to use the AISC Specifications because its Preface does reccmunend the use of the AISI's " Specification for the Design of Cold-Fomed Steel Structural Members." Therefore, where applicable, NES' design does confom to the AISI cold-fomed steel specification as modified to include the stainless steel material properties.5 NES detemines that confomance to the AISI Specification assures confomance l to the princa. pal AISC Specification.

c. WalM ng Requirements All rack walM"5 confoms to the design and fabrication requirements of I the ASME Code with the exception of the are spot welds used in the l

storage cell fabrication. Since the storage cells are fabricated from thin cold-fomed stainless steel, the provisions of the AISI Specification apply as discussed in paragraph b.above. Per paragraph 4.2 of the AISI Specification, resistance spot welding is an acceptable method for joining sheet metal when perfomed in accordance with AWS' " Recommended Practices for Resistance Spot Welds."

Paga 3 of 5 However, the use of welding processes other than those specifically mentioned is allowed, provided they are qualified by applicable tests and approved by the Engineer. This allowance is so stated in paragraph 13.4 of the General Provisions of the AWS " Structural Welding Code -

Steel", the AISC's governing welding code.

To establish the justification for the use of gas tungsten-arc spot welds, it should be noted that it states in the AWS Welding Handbock that this process "...is quite versatile and can be used to produce excellent quality spot welds." The use of gas tungsten-arc spot velds for storage cell fabricaticn per AISC requirements is therefore justified.

The welds were perfomed in accordance with the AWS' "Reccamended Practices for Gas Tungsten Arc Welding"9 and the welding procedures were qualified by suitable tests establishing veld strength and proces3 requirements to consistently achieve good welds. Therefore, all rack welding is in full compliance with the AISC Specification requirements.

d. Clarification of Material Certificatien and Traceability l As required by paragraph NF-2121 of Subsection NF of the ASNE Code, all material used in the fabrication of the Calvert Cliffs racks confoms to the requirements of the specifications for materials

:ted in the applicable tables of Appendix I of the ASME Code.

Certification of empliance to the above requirements is assured i

through Certified Material Mill Test Reports furnished for all stai .

l less steel used in the fabrication.

Paga h of 5 Traceability of materials used in individual rack ccmpenents is maintained thrcugh assurance that all items utilized during fabrication are fra a single controlled lot of certified =aterial from several heats.

These methods of certification and traceability are consistent with the requirements of Subsection NF paragraphs NF-213o and riF-2150 for Class 2 fabrication and further cca:: ply with 10 CFR Part 50, app *M4v 3, Criteria VII and VIII, for identificatica and centrol of =aterial.

o Paga 5 of 5 REFERI2fCES

1. "2 Pesition for Review and Acceptance of Spent Fuel Storage and hailing Applications," Nuclesr Regulatory Ccamissica (April,1978)

2. " Specification fcr the Design, Fabrication and Erection of Structural Steel for h41 dings," American Institute of Steel Ccnstruction (November,1978) 3 "3ciler and Pressure Vessel Code," American Society of Mechanical Engineers,Section III, Subsection NF and Appandir XVII (1977 Edition) 4.

" Specification for the Design of Cold Fezzed Steel Structural Members,"

American Iron and Steel Institute (1968 Editien) 5 " Specification for the Design of Cold Formed Stainless Steel Structural Members," American Iren and Steel Institute (1974 Edition)

6. "Reccamended Practices for Resistance Welding," American Welding Society, NAS C1.1-66

7. " Structural Welding Code-Steel," American Wciding Society, AWS Dl.1-79

8. " Welding Handbook," American Welding Society l

9 "Reccamended Practice for Gas Tungsten Arc Welding," American Welding Society, AWS C5 5-80

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